Railway car roll control system

ABSTRACT

This invention relates to a control system for controlling rotation or roll about a longitudinal axis of a variable trim railway vehicle body, so as to compensate for lateral acceleration as the vehicle moves over a curved track. A gyroscope records tilt of an axle about a longitudinal axis of the vehicle and the gyroscope signal, after integration, is passed through a threshold device to a gate or switch to open the latter at a predetermined threshold level and thereby cause a rate signal, derived from a tachometer on the vehicle, to be transmitted to a servomechanism for rotating the vehicle body.

United States Patent 11 1 Di Majo [4 1 Oct. 29, 1974 Franco Di Majo,Turin, Italy [30] Foreign Application Priority Data FOREIGN PATENTS ORAPPLICATIONS 2,204,072 8/1972 Germany Primary ExaminerM. Henson Wood,Jr.

Assistant Examiner-Howard Beltran Attorney, Agent, or FirmSughrue,Rothwell, Mion, Zinn and Macpeak 5 7] ABSTRACT determined thresholdlevel and thereby cause a rate signal, derived from a tachometer on thevehicle, to be transmitted to a servomechanism for rotating the vehiclebody.

1 6 Claims, 18 Drawing Figures Feb. 9, 1971 Italy 67426/71 [52] US. Cl105/164, 105/199 R, 105/210, 280/61 [51] Int. Cl B60g 21/04, B61f 3/00,B61f 5/24 [58] Field of Search 105/164, 199 R, 210', 280/6.1

[56] References Cited UNITED STATES PATENTS 2,568,402 9/1951 Lynn105/164 X 2,633,811 4/1953 Poage 105/164 X 3,083,027 3/1963 Lindblom280/61 3,683,818 8/1972 Meir et al. 105/164 PATENTEDUBIZQ 1914 3.844225sum 3 0f 6 I Fig-6 30 32 4 36 I I a W 38 m I72 170 59 60 56 58 T/MEE U hE Pmmanums m4 3344.225

. SHEET M]? 6 I 1 RAILWAY CAR ROLL CONTROL SYSTEM BACKGROUND OF THEINVENTION This invention relates to railway vehicle trim controlsystems, applicable to a railway vehicle having a body which is adaptedfor controlled rotation about a longitudinal axis.

Railway vehicles with variable lateral trim are known, in which thevehicle body, when travelling around a curve, is'made to rotate about alongitudinal axis so as to counterbalance, with a component of itsweight, the centrifugal force acting upon the vehicle, so that thepassengers experience, even at high speed, a relatively limited lateralacceleration ideally between 0.6 and 1.0 m/sec (2-3 ft/sec).

The simplest form of such compensation is where the vehicle body issuspended pendulum-fashion and is freely rotatable about thelongitudinal axis, this axis being higher than the centre of gravity ofthe body. When the vehicle travels around a curve the body rotates underthe action of the centrifugal force to an equilibrium position in whichthe centre of gravity of the body lies on the resultant of thecentrifugal force and the weight, so that no lateral reaction isexperienced by any vehicle passenger.

Such a simple pendulum system has been little used in practice since ithas the disadvantage that the body rotates about its axis under theinfluence of the centrifugal force at too low an acceleration, onaccount of the high inertia of the suspended body, and consequently thebody cannot reach its position of equilibrium within the usualrelatively short time during which the vehicle is travelling over thetransition sections of a track between straight and fully cambered curvesections. Compensation for the centrifugal force is complete in the fullcurve, but inadequate along the transition portions of the track, andconsequently the passengers may experience intense lateral accelerationas the vehicle travles over the transition portions, which is veryunpleas ant even though of short duration.

Consequently servo-assisted rotation control systems are favoured, inwhich, by the use of sufficiently powerful and fast-actingservo-controls, the vehicle body can be rotated by the required amountat each stage of its movement around a curve.

In early assisted rotation control systems, intervention of theservo-controls is controlled in response to lateral acceleration of thevehicle body, sensed, for example, by a pendulum with a longitudinalaxis, or by an accelerometer mounted on the vehicle body.

With such systems, however, no means exist for ascertaining whether thesensed lateral acceleration results from centrifugal force, or fromdisturbances caused by irregular motion of the vehicle. In particular,the lateral oscillation or snaking" phenomenon which is nearly alwaysexhibited by a moving railway vehicle could give rise to undesirableintervention of the servocontrol system. In order to avoid this, it isnecessary to damp the movement of the pendulum, or to filter theaccelerometer output signal, to exclude lateral accelerations of highfrequency. Such measures, however, result in a slowing down of theresponse to the rotation control system and a reduction in the timeavailable for carrying out the actual trim variation. In practice, theavailable time is very short, particularly for a high speed railwayvehicle.

Thus a vehicle travelling at 200 Km/h (I24 mph) covers a parabolictransition track 1 l0 metres (361 ft.) long between a straight and afull curve track section in about 2 seconds. In this time it isnecessary to detect the presence of the curve and bring theservo-control into action to rotate the whole body about a longitudinalaxis. This rotation clearly must include a phase of angular accelerationand a phase of angular deceleration. It will therefore be apparent thatit is necessary to reduce to a minimum the delay between the start ofthe track curvature and occurrence of the variation in trim under theaction of the servo control system.

A similar problem arises at the end of a curve, in the transition tracksection between a fully curve and a straight track section.

This problem with which the present invention is concerned isillustrated graphically in FIGS. 1 to 4 of the attached drawings.

FIG. 1 shows the lateral acceleration acting upon a vehicle body (curveI), travelling over a curve in a railway track at constant speed,plotted against time, and also the compensated lateral acceleration(curve II) of the said body when the body is rotated about alongitudinal axis, in the case where, as usually occurs in practice, theangle of rotation of the body is, for reasons of construction and bulk,limited to angles less than a certain maximum angle, so that lateralacceleration is not wholly compensated;

FIG. 2 shows the variation in amplitude a of a typical non-filteredsignal derived from an accelerometer and representing the lateralacceleration shown in curve 1 of FIG. 1;

FIG. 3 shows the accelerometer signal of FIG. 2 after filtering withupper cut-off frequency equal to 0.5 Hz(cps) and after retardation by anoverall delay of one second, and

FIG. 4 shows the lateral acceleration a felt by the passenger whenrotation of the vehicle body about the longitudinal axis is controlledon the basis of the signal of FIG. 3, also plotted against time.

The actual rotation of a vehicle body under control of a signal of thetype shown in FIG. 3 will be further retarded by 0.1 0.2 sec., due tothe response time to the rotation servomechanism, so that, taking thediffer ence between the centrifugal acceleration and the rotation of thebody, one will have, for the lateral acceleration a experienced by thepassenger, a very uneven pattern, certainly not conducive to comfort, asshown in FIG. 4, where the highest permissible lateral accelerationlevel is indicated by a broken line at about 0.08g.

A main object of this invention is to provide a rotation control systemfor the body of a railway vehicle with variable lateral trim, which iscapable of detecting with a minimal delay (around 0.1 0.2 seconds) thestart and finish of a curve in a railway track along which the vehicleis travelling, including the transition track sections at the entry toand exit from the curve, and which is adapted to cause rotation of thevehicle body about a longitudinal axis to compensate for the lateralacceleration of the vehicle as it passes over the track, so thatpassengers are not subjected to accelerations greater than apredetermined threshold.

SUMMARY OF THE INVENTION According to the invention there is provided acontrol system for controlling the rotation of a railway vehicle bodyabout a longitudinal axis as the vehicle travels along a curved track,comprising a gyroscope adapted to be mounted in relation to an axle ofthe vehicle so as to be responsive to and to provide an output signalrepresentative of tilt of the axle about a longitudinal axis of thevehicle, an integrator arranged to integrate said gyroscope outputsignal, signal forming means including a tachometer responsive to thevehicle speed for providing a rate signal determining a desired rate ofrotation of the vehicle body, said rate signal being supplied to aservomechanism for effecting rotation of the vehicle body through a gateor switch which is controlled by an enabling or control signal providedby a threshold device when the output of the integrator reaches apredetermined threshold level.

The integrator is preferably of the type whose output signal returns tozero when the input signal is removed.

According to a further preferred embodiment of the invention thethreshold device is connected to the gate through a persistence deviceadapted to prolong the output signal of the threshold device by apredetermined time interval following the end of the said output signal.Preferably the system is normally controlled by the rate signal from thesignal forming means, and in which the system is controlled, after apredetermined time from the detected start of a curve in the track, bythe output signal of a chain including, in series, a first lateralaccelerometer arranged, in use of the system, on a bogie of the vehicle,a first low-pass filter, and a differentiator.

The control system may also include a second lateral accelerometermounted on the vehicle body, a second low-pass filter connected to theoutput of the second accelerometer, and a second threshold deviceconnected to the output of the low-pass filter, the second thresholddevice being connected to the servomechanism through a gate which iscontrolled by the output of the first threshold device applied to thegate through an inverter.

THE DRAWINGS ILLUSTRATING THE INVENTION FIG. I is of a graph showing thelateral acceleration acting upon a vehicle body (curve I), travellingover a curve in a railway track at constant speed, plotted against time,and also the compensated lateral acceleration (curve ll) of the saidbody when the body is rotated about a longitudinal axis in the casewhere the angle of rotation of the body is limited to angles less than acertain maximum angle so that the lateral acceleration is not whollycompensated;

FIG. 2 is a graph showing the variation in amplitude of a typicalnon-filtered signal derived from an accelerometer representing thelateral acceleration shown in curve I of FIG. 1;

FIG. 3 is a graph showing the accelerometer signal of FIG. 2 afterfiltering with upper cut-off frequency signal equal to 0.5Hz and afterretardation by an overall delay of one second;

FIG. 4 is a graph showing the lateral acceleration felt by a passengerwhen rotation of the vehicle body about the longitudinal axis iscontrolled on the basis of the signal of FIG. 3:

FIG. 5 shows diagrammatically in perspective part of a bogie or track ofa railway vehicle equipped with a lateral trim control system accordingto the invention;

FIG. 6 is a block schematic diagram of one embodiment of a controlsystem according to the invention;

FIG. 7 is a circuit diagram of one of the blocks in the diagram of FIG.6;

FIG. 8 is a block schematic diagram of a second embodiment of a controlsystem according to the invention;

FIG. 9 is a block schematic diagram of a third embodiment of a controlsystem according to the invention;

FIG. 10 illustrates diagrammatically in elevation the camber of a curvedrailway track, and

FIGS. 11 17 represent diagrammatically the waveforms of differentsignals in the control system accord ing to the invention, plottedagainst time, illustrating the operation of the system.

FIG. 18 is a cross-sectional view of a railway vehicle showing therelationships of the axle, wheels, gyroscope and tachometer relative toa vehicle body and servo-mechanism, the body and servo-mechanism beingshown in phantom lines.

DETAILED DESCRIPTION OF THE INVENTION FIGS. 5 and 18 show two wheels l0,12 of a railway vehicle (not shown) connected by an axle 14. A bridge 16which supports the body 41 of the railway vehicle is carried by the axlel4.

The bridge 16 carries a housing 18 in which a gyroscope (not shown inFIG. 5) is mounted, the axis of ro tation of the gyroscope beingcontained in a vertical transverse plane of the vehicle and beingoriented in said plane in a direction preferably parallel to ororthogonal to the axis of rotation b b of the axle 14. That is to say,the axis of rotation of the gyroscope is either along the axis a a oralong the axis d d of FIG. 5. In any event, the gyroscope is arranged insuch a way as to register the tilt of the axle 14 or of the bogie onwhich the axle is carried in the said transverse vertical plane, thatis, about a longitudinal axis c c.

The suspension of the gyroscope housing 18 consists of a shaft 22rotatably supported by two brackets on the bridge 16 and arrangedparallel to the axis b b of the axle 14, and two arms 24, 26 fixed tothe shaft 22 and pivotally connected at their free ends to the housing18 by means of coaxial pins 25, 27 integral with the housing 18, thecommon axis of the pins 25, 27 being aligned with the axis a a.

The housing 18 rests on a flat portion of the bridge l6 by way of aninterposed resilient pad 28. The housing 18 could alternatively bemounted on the frame of one of the bogies of the railway vehicle or anyother suitable place on the truck or running gear.

In this way the axis a a of the housing 18 always remains parallel tothe axis b b of the axle 14. The resilient pad 2 protects the gyroscopeagainst vibrations and high frequency dynamic forces, whilst thesuspension of the gyroscope housing 18 supports the'housing 18 againstlateral and longitudinal movement, leaving it free to move vertically,that is, by rotation about the axis of the shaft 22. The axis a a of thegyroscope therefore remains constantly parallel to the axis b b of theaxle 14, whilst still being able to effect displacement parallel to theaxle I4. Consequently the signal generated by the gyroscope will beproportional only by the torque acting on the gyroscope in the verticalplane, due -to tilt of the axle 14 about the longitudinal axis c c, as aresult of camber of the track, that is, superelevation of one rail ofthe track relative to the other.

FIG. illustrates diagrammatically the variation in camber of a railwaytrack having a curved path, represented as the variation with time t ofthe height h or superelevation of one rail relative to the other for ageometrically perfect pair of rails laid in a curve, as experienced by avehicle passing over the track at constant speed. In other words, FIG.10 represents diagrammatically the elevation E of the outside rail asviewed from the inside rail of the curve. The central portion of thecurve, shown parallel to the axis t in FIG. 10 is the full curve portionof constant camber, and in this portion, and in the straight portions ateach end of the curve, the track has a constant camber, so that thespeed of tilt of a vehicle axle about the longitudinal axis of thevehicle is zero in these portions. In the transition sections of track,however, at the entry to and exit from the full curve portion, the speedof tilt T of the axle about the longitudinal axis of the vehicle wouldideally be constant and equal in each case to iV/S, where i is thegradient, in mm/metre or inches foot, of the outside track relative tothe inside track of the curve, S is the distance in mm. or inchesbetween the bearing points of the vehicle wheels on the two respectiverails that is, the gauge of the track and V is the speed of the vehiclein m/sec. (or ft./sec).

The gyroscope output signal representing the speed of rotation of theaxle about the longitudinal axis of the vehicle would therefore ideallyhave the form indicated in FIG. 11.

In practice, however, the rails of the track have an unevenness whichboth on straight and on full curve (constant camber) portions give riseto lateral tilt of the vehicle axle about the longitudinal axis of thevehicle, these variations being superimposed upon those due to thechange in camber of the track in the transition sections, so that theresultant gyroscope output signal has the form shown in FIG. I2.

In order to avoid untimely intervention of the trim control system, thesignal determining the start of the compensating rotation of the vehiclebody is not the angular velocity of the axle about the longitudinal axisbut the integral in time of the said speed when this is higher than acertain value.

The integration of the angular velocity signal gives a signal related tothe angle of the axle to the horizontal, or, multiplying by 8", thesuperelevation h of one rail (the outside rail of the curved track)relative to the other.

In practice. even with the most perfect integrating instrument theresulting iiitegral does not maintain a fixed zero line, but undergoes aprogressive drift", so that after a certain time there is no longer anycorrespondence between the integrated signal and the effectivesuperelevation h.

In order to avoid this, and to provide a signal which will indicatereliably and promptly the varying camber transition sections adjoining acurvedtrack the control system shown in FIG. 6 is used.

In FIG. 6, 30 indicates the gyroscope mounted in the housing 18 in FIG.5. The gyroscope 30 provides a velocity signal representative of theangular velocity of the axle 14 about a longitudinal axis C C (FIG. 5)of the vehicle. This angular velocity signal is passed to a limiter 32which cuts off this signal at a maximum amplitude corresponding to thehighest rotational speed of the axle 14 about the axis CC due to trackcamber or superelevation (about 0.08 rad/sec. In this way one excludeshigh transitory values of h caused by, for example, localised subsidencebelow individual sleepers of the track, or by points in bad condition.

The output signal from the limiter 32 is passed to an integrator 34, ofthe type in which the integral is returned to zero every time the inputsignal, that is to say the limited angular velocity signal, goes throughzero. An integrator of this type is described in the Applicants GermanPatent Application filed Offenlegungsschrift. published Aug. I0, 19722204072. The output of the integrator 34 therefore has the form shown inFIG. 13.

A threshold 11,, is fixed below which the integrated signal does notgive rise to any effective control signal. The threshold 11 must be alittle greater than the value of the integrator output corresponding tothe greatest track inclination and constitutes the threshold value of athreshold device 36. The threshold device 36 receives the output of theintegrator 34 and provides a constant amplitude positive or negativesignal g whenever the integrator output exceeds a positive or negativethreshold level respectively indicated by the dashed lines h and h inFIG. 13. The output of the threshold device 36 is represented in FIG.14.

A persistence device 38 (FIG. 6) provides an output signal P consistingof positive or negative constant amplitude pulses or duration At (0.100.15 sec), each pulse originating immediately after the output of thethreshold device 36 drops to zero, thus eliminating the disadvantage offrequent disappearance of the signal if the track curve is in a badcondition, and has points at which the track camber is constant and thensuddenly reverses. The contribution made by the persistence device 38 isrepresented in FIG. 15; this contribution is added to the output of thethreshold device 36 (FIG. 14) to give a combined output signal C asshown in FIG. 16.

A tacho-generator 52 installed on the vehicle to record its speed oftravel supplies a tachometer signal to a forming circuit 52' whichdetermines the speed of rotation of the vehicle body which, as describedbelow, gives an output rate signal representative of the desiredrotational speed of the body, the magnitude of which is dependent uponthe speed of the vehicle.

The rate signal ouput of the forming circuit 52 provides one input 39aof an AND gate 39, the enabling or control input 39b of which consistsof the output signal of the persistence device 38. When the gate 39 isopened by the control input 3% it passes the rate signal from theforming circuit 52' to a servomechanism 40 controlling the rotation ofthe vehicle body about the longitudinal axis, so that the body is thenrotated at a predetermined rate, related to the speed of the vehicle.

The servomechanism 40 as shown in FIG. 18 may be of known type, eitherelectric or hydraulic, and should preferably include counter-reactive(negative feedback) means for more exact positioning of the body 41. Thecombined output signal of FIG. 16 has a value of other than zero onlyduring travel of the vehicle along the transition track sections andeach pulse of this signal is delayed relative to the start and thefinish of the said transition sections by intervals of very shortduration (0.1 0.2 sec.). As soon as this signal is detected, the vehiclebody is rotated by the-servomechanism 40 in the same direction as thatin which tilt of the axle 14 is sensed. Upon cessation of the signalrotation of the body by the servomechanism 40 is also stopped.

In FIG. 7 there is shown a simplified circuit diagram of a preferredembodiment of the forming circuit 52' which includes a number ofdifferential amplifiers 2004, 200-2, 200-n. Each of the differentialamplifiers has a positive input consisting of a tachometric signal Vprovided by the tachometer 52 and a negative input consisting ofrespective fixed fiducial voltages V V V,,, of successively increasingvalue. The respective outputs of the amplifiers 200-J, 200-2, 200-n areconnected to earth via Zener diodes 202I, 202-2, 202-n and are alsoconnected to a common point 204 through the respective resistors 206-1,2062, 206-n. An output operational amplifier including an amplifier 208and resistors 210, 212, amplifies with calibrated gain the combinedoutput signal present at the point 204, determining the rate of rotationapplied to the body.

The contribution to the combined output signal at point 204 provided byeach amplifier 200 and Zener diode 202 is zero when the tachometricsignal V is less than the respective fiducial voltage V V V,, while itis positive and constant when the tachometric signal V is greater thanthe fiducial voltage V, V,,. Therefore the output signal V of theamplifier 208 increases in a stepwise manner in relation to thetachometric signal V, as illustrated graphically in FIG. 17. Theparameters which define the graph of FIG. 17 are, for example, thoserecorded in the following table, where V is the speed of the vehicle,and 0 the corresponding angular speed of rotation required of the body.

The integrated gyroscopic signal determines the duration of the rotationapplied to the body; for a vehicle moving along parabolic transitiontrack sections it is necessary. by means of other controls, to regulatein a more exact fashion the speed of rotation of the body.

Since the angle of rotation of the body has to be proportional to thenon-compensated lateral acceleration a due to the camber of the track itis necessary that the speed of rotation of the body shall also beproportional to the rate of variation of the said acceleration FIG. 8shows the block diagram of a system of rotational control of the bodyfor achieving such a proportional rate of rotation. A lateralaccelerometer 44 is mounted on the bogie of the vehicle to record itslateral acceleration. The output signal of the accelerometer 44 passesthrough a low-pass filter 46, which filters the signal with an uppercut-off frequency of 0.5 Hz. The output signal of the filter 46 ispassed through a differentiator 48 to give a signal proportional to therate of change of the lateral acceleration, this rate signal beingstored in a memory which has a set/reset input 152.

The tachometric output signal of the forming circuit 52 is passed to afirst input of a two-position selector switch 154, a second input ofwhich receives the output of the memory 150. The selector switch 154normally transmits the tachometric signal from the forming circuit 52 toan output point 156. A timer 158, controlled by the output signal of thepersistence device 38, supplies, after a predetermined time of about onesecond from the start of the track curve, a control signal to theselector switch 154 in order to commute the switch 154 to the secondinput, passing to the output point 156 the stored signal from the memory150, and at the same time activating the memory 150 to store the valueof the signal at its input at that instant.

The AND gate 39 in FIG. 6 is in FIG. 8 replaced by a three-positionselector switch 160. The selector switch 160 is arranged to transmit tothe servomechanism 40 the output signal from the selector switch 154either directly or after inversion in an inverter 162, according to theposition of the switch 160, which is determined by the output signal ofthe persistence device 38, supplied via line 164. When the output of thepersistence device 38 is zero, the selector switch 160 is in its neutralposition, as shown in FIG. 8', when the output of the device 38 ispositive the selector switch 160 transmits the output signal from switch154 direct to the servomechanism 40, and when the output of the device38 is negative the selector switch 160 transmits the inverted outputsignal to the servomechanism 40.

Control of the rotation of the body about the axis C-C therefore takesplace in two'phases.

In the first phase, no signal reaches the memory 150 from the lateralaccelerometer 44, since the low-pass filter 46 introduces a delay ofabout one second in the output signal of the lateral accelerometer 44.Rotation of the body therefore occurs in the first phase under thecontrol of the forming circuit 52' only, as in the schematic arrangementshown in FIG. 6.

When a period of about one second has elapsed from entry into the curve,the signal proportional to the rate of change of non-compensated lateralacceleration a,,,. reaches the memory 150 from the differentiator 48 andsimultaneously the memory 150 is activated, together with commutation ofthe selector switch 154. Rotation of the body now continues under thecontrol of the output signal from the lateral accelerometer 44.

FIG. 9 shows a more complete embodiment of a system of rotationalcontrol of the body of a railway vehicle about a longitudinal axis. Inaddition to the components of the system of FIG. 8, the system of FIG. 9includes a lateral accelerometer 56 which registers the residualtransverse acceleration a acting upon the body. In this case, too, theoutput signal of the accelerometer 56 is passed through a low-passfilter 58 with a cut-off frequency of 0.5 Hz(cps). The output signal ofthe filter 58, which is proportional to a is passed to a thresholddevice 59 adapted to provide a predetermined calibrated signal which ispositive or negative according to whether the output signal of theaccelerometer 56 is positive or negative respectively. This calibratedsignal is passed via an AND gate 60 to provide an alternative input tothe servomechanism 40. In effect the output of the AND gate 60 and theoutput of the selector switch 160 are connected to the servomechanism 40via an OR gate. The AND gate 60 has a control input constituted by theoutput signal of the persistence device 38, inverted by means of aninverter 171.

In contrast to the embodiment of PK]. 8, the persistence device 38 inthe embodiment of FIG. 9 is not directly connected to the output of thethreshold device 36, but is connected to the latter through one or tworoutes: one, direct, route comprises an AND gate 166 having a controlinput constituted by the output signal of the threshold device 59,inverted by an inverter 168; the other. indirect, route comprises a time170 and an AND gate 172 having a control input constituted by thedirectly applied output signal of the threshold device 59 The outputsignal of the AND gate 60 when applied to the servomechanism 40 causesreverse rotation of the body back into the normal position, with a verylow speed, of the order of 0.005 rad/sec. This serves the purpose ofreturning the body to its normal position when the speed of the vehicledecreases as the vehicle moves along a curve of constant radius, or whenthe gy roscopic signal is nil, for example if the vehicle stops on acurve.

The timer 170 interposed between the threshold device 36 and thepersistence device 38 only works if the residual transverse accelerationa has a sign conflicting withthe gyroscopically sensed acceleration, andhas the object of introducing a delay very roughly proportional to theacceleration a acting upon the body, between perception of theintegrated gyroscopic signal and the start of the rotation of the body.In this fashion the rotation imparted to the vehicle body approximatesas closely as possible to the variation with time of the non-compensatedacceleration a and one can reduce to a minimum the end of track phasedisplacement in the case in which the compensation of the lateralacceleration is not complete.

I claim:

1. A control system for controlling the lateral trim of a railway bodywhich is rotatable about a longitudinal axis on a supporting truck inwhich at least one vehicle axle is supported for rotation as the vehicletravels along a curved track, said system comprising;

a gyroscope mounted on said truck in close relation to said axle of thevehicle for providing an electrical output signal representative of thetilt of said axle about a longitudinal axis of the vehicle, integratormeans connected to said gyroscope for integrating said output signal,said integrator means being of the type whose output signal returns tozero when the input signal is removed,

a threshold device connected to the integrator means to provide anenabling control signal when the integrated signal reaches apredetermined threshold level,

signal forming means including a tachometer adapted to be mounted on thevehicle to provide a signal representative of the vehicle speed, saidsignal forming means providing from said speed signal a rate signaladapted to be applied to a servo mechanism for effecting the desiredrate of rotation of the vehicle body about a longitudinal axis of thebody in response to said rate signal,

gating means connected to said first forming means and having a controlinput connected to said threshold device whereby said gating means isadapted to pass said rate signal to said servo mechanism when saidthreshold device produces the enabling control signal,

said system further comprising in series, a first lateral accelerometeradapted to be mounted upon said truck of the vehicle, a first low-passfilter, and a differentiator, said system being controlled after apredetermined time from the detected start of a curve in the track, bythe output signal of said differentiator.

2. The control system claimed in claim 1 and further including a limiterconnected at the input of the integrator means and limiting theamplitude of the gyroscope output signal which is integrated toamplitudes less than the greatest possible angular speed of rotation ofthe said vehicle axle about said longitudinal axis when the vehicle ismoving over a curved track.

3. The control system claimed in claim 1, including a persistence devicethrough which the threshold device is connected to said gating means,said persistence device prolonging the output signal of the thresholddevice by a predetermined time interval following the end of the saidoutput signal.

4. The control system claimed in claim 1, and further including a secondlateral accelerometer adapted to be mounted on the vehicle body, asecond low-pass filter connected to the output of the secondaccelerometer, and a second threshold device connected to the output ofsaid low-pass filter, a gate controlled by the output of said firstthreshold device and an inverter interposed between said gate and saidfirst treshold device, said second threshold device being connected tosaid servomechanism through said gate.

5. The control system claimed in claim 4, and further including apersistence device through which the threshold device is connected tosaid gating means, said persistence device prolonging the output signalof the threshold device by a predetermined time interval following theend of the said output signal, a delay circuit interposed between saidfirst threshold device and said persistence device and controlled by'the output signal of said second threshold device to cause a delay inthe application of the enabling control signal to the gating means whenthe output signal of said second threshold device is greater than thethreshold level.

6. The control system claimed in claim 1, in which said gating means isa selector switch the operation of which is controlled by said controlinput from said threshold device.

1. A control system for controlling the lateral trim of a railway bodywhich is rotatable about a longitudinal axis on a supporting truck inwhich at least one vehicle axle is supported for rotation as the vehicletravels along a curved track, said system comprising; a gyroscopemounted on said truck in close relation to said axle of the vehicle forproviding an electrical output signal representative of the tilt of saidaxle about a longitudinal axis of the vehicle, integrator meansconnected to said gyroscope for integrating said output signal, saidintegrator means being of the type whose output signal returns to zerowhen the input signal is removed, a threshold device connected to theintegrator means to provide an enabling control signal when theintegrated signal reaches a predetermined threshold level, signalforming means including a tachometer adapted to be mounted on thevehicle to provide a signal representative of the vehicle speed, saidsignal forming means providing from said speed signal a rate signaladapted to be applied to a servo mechanism for effecting the desiredrate of rotation of the vehicle body about a longitudinal Axis of thebody in response to said rate signal, gating means connected to saidfirst forming means and having a control input connected to saidthreshold device whereby said gating means is adapted to pass said ratesignal to said servo mechanism when said threshold device produces theenabling control signal, said system further comprising in series, afirst lateral accelerometer adapted to be mounted upon said truck of thevehicle, a first low-pass filter, and a differentiator, said systembeing controlled after a predetermined time from the detected start of acurve in the track, by the output signal of said differentiator.
 2. Thecontrol system claimed in claim 1 and further including a limiterconnected at the input of the integrator means and limiting theamplitude of the gyroscope output signal which is integrated toamplitudes less than the greatest possible angular speed of rotation ofthe said vehicle axle about said longitudinal axis when the vehicle ismoving over a curved track.
 3. The control system claimed in claim 1,including a persistence device through which the threshold device isconnected to said gating means, said persistence device prolonging theoutput signal of the threshold device by a predetermined time intervalfollowing the end of the said output signal.
 4. The control systemclaimed in claim 1, and further including a second lateral accelerometeradapted to be mounted on the vehicle body, a second low-pass filterconnected to the output of the second accelerometer, and a secondthreshold device connected to the output of said low-pass filter, a gatecontrolled by the output of said first threshold device and an inverterinterposed between said gate and said first treshold device, said secondthreshold device being connected to said servomechanism through saidgate.
 5. The control system claimed in claim 4, and further including apersistence device through which the threshold device is connected tosaid gating means, said persistence device prolonging the output signalof the threshold device by a predetermined time interval following theend of the said output signal, a delay circuit interposed between saidfirst threshold device and said persistence device and controlled by theoutput signal of said second threshold device to cause a delay in theapplication of the enabling control signal to the gating means when theoutput signal of said second threshold device is greater than thethreshold level.
 6. The control system claimed in claim 1, in which saidgating means is a selector switch the operation of which is controlledby said control input from said threshold device.